r1

1. Definition of Plastics

ØThermoplasticsØPolymers that are converted into shapes

by processes involving flow of liquid (molten) polymer before solidificationØMust melt at a reasonable temperatureØMust be flowable when moltenØMust be easily shaped or fabricated

2. Plastics FabricationØ Compression molding – also used for thermosetsØ Polymer powder or monomers placed in one half of moldØ Application of pressure and heating melts polymer (or causes

monomers to react) to form shape of moldØ Cross-linking can occur, especially for thermosets

3. Plastics FabricationØVacuum moldingØHot polymer sheet placed over top of moldØVacuum pulls polymer to walls of chilled mold

4. Plastics FabricationØ Injection molding of thermoplasticsØGranular polymer melted in heated screwØForced through an opening directly into cooled mold

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5. Plastics FabricationØ Injection molding of polyurethane (thermoset)

resins (reaction injection molding or RIM)ØSeparate compartments for polyol and isocyanateØFed into the mold where polymerization takes place

6. Plastics FabricationØExtrusionØForcing molten polymer through a die (shaped

opening) Polymer pellets

7. Plastics FabricationØBlow moldingØMolten polymer extruded through circular die to form

bubble or parisonØAir injected, forcing polymer to walls of the cooled

mold

8. Plastics FabricationØBlown filmØMolten polymer forced

through circular dieØAir flow forms bubble,

shape controlled by cooling ringØBubble can be 7 ft in

diameter and > 30 ft tallØBubble collapsed via

rollers to form wide sheets (films)ØSheets rolled up for

further cutting and sizing

AIR RING TOCOOL PLASTIC

DIE

AIR INLET

FLATTENING ROLLS

NIP ROLLS

BLOWN TUBE

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9. Plastics FabricationØExtrusion coatingØMolten polymer extruded onto cooled substrateØForms solid film instantly upon contact with substrate

10. Plastics FabricationØCast film formationØMolten polymer extruded onto chilled rollØForms solid film instantly upon contact with roll

11. Plastics FabricationØCalenderingØMolten polymer pressed into thin film by passing

through rollers with increasingly more narrow gaps

12. Plastics FabricationØWire and cable coating

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13. General Plastics Uses

Containers, lids, film

Piping, siding, fittings

Plywood adhesives

Packaging 32%Building and construction 14

Consumer products 13Electrical equipment 6

Furniture 5Transportation equipment 4

Miscellaneous 26

Uses of Thermoplastics

Building and construction 69%Transportation equipment 8

Adhesives, coatings 4Consumer products 4Electrical equipment 4

Miscellaneous 11

Uses of Thermosets

14. Definition and ClassesØPlasticØPolymers that are converted into shapes by

processes involving flow of liquid (molten) polymer before solidification

ØPlastics can be identified and characterized by the shape of their stress-strain curvesØHard-toughØHard-strongØHard-brittleØSoft-toughØSoft-weak

15. Stress-Strain Curve

Slope = measure of stiffnessYoung’s Modulus

Area under curve = total energy to breakLarger area = tougher polymer

16. Stress-Strain Curve

Strain (% elongation)

Str

ess

(psi

)

Yield elongation

Yield point

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17. Stress-Strain Curve

Elastomers Plastics FibersModulus (psi) 15 - 150 1,500 - 200,000 150,000 - 1,500,000Percent Elongation 100 - 1000 20 - 100 < 10Crystallinity Low Moderate HighPolymer example Natural rubber Polyethylene Nylon

18. Definition and ClassesØHard = high modulus (steep slope)ØTough = high elongationØStrong = moderate elongation and high modulus

High High High High High density polyethyleneCellulosicsPolyamides (Nylon)PolyestersPolypropyleneEngineering plasticsPolyacetal, polycarbonate

Hard and tough

Polyimide, polyphenylene sulfide, polyphenylene oxidePolysulfone

High High High Moderate

Poly(vinyl chloride) PVCImpact polystyrene

Hard and strong

Styrene-acrylonitrile

Elongation at Break Examples

Class of Plastic Modulus

Yield Stress

Ultimate Tensile

Strength

19. Important PlasticsØHard and toughØHigh density polyethylene, HDPE ØManufacture ?

ØPropertiesØLittle branching (< 7 per 1000 C atoms)ØHigh crystallinity (Tm = 135 oC, Tg = -70 to – 20oC)ØRelatively opaqueØRelatively stiff, hard with high tensile strengthØDensity > 0.94 g/cc

(CH2 CH2)n

20. Important PlasticsØHard and toughØHigh density polyethylene, HDPE

ØEconomicsØ12.5 billion pounds produced in 2001ØCurrently about $0.48 per poundØCommercial value = $6.0 billionØRecent growth rate: 5 – 6% per year, except for 2001ØHeavily recycled

Blow molding 35%Injection molding 22

Film 17Pipe and conduit 14

Sheet 6Wire and cable 1Miscellaneous 5

Uses of HDPEBottles, gas tanks

Crates, pails, toys

Packaging

Water and sewer, low pressure gas distribution

(CH2 CH2)n

r6

21. Important PlasticsØHard and toughØPolypropylene, PPØManufacture ?

ØWhat does isotactic mean?

ØPropertiesØStiffer, harder, higher tensile strength than HDPEØTm = 170 oC, Tg = -10 oC (brittle at low temperatures)ØMore degradable by heat, light and O2 than HDPE due to ?

_______________________________ØStabilizers and antioxidants are requiredØDensity = 0.91 g/cc

(CH2 CH)n

CH3

22. Important PlasticsØHard and toughØPolypropylene, PP

Ø EconomicsØ16 billion pounds produced in 2001ØCurrently about $0.34 per poundØCommercial value = $5.4 billionØRecent growth rate: 6.5 % per yearØRecycling may become important

(CH2 CH)n

CH3

Injection molding 31%Fibers and filaments 30

Distributors and compounders 23Film and sheet 11Blow molding 2Miscellaneous 3

Uses of PPContainers, toys, furniture

Carpet backing, carpet fibers, ropes

23. Important PlasticsØHard and tough

ØPoly(ethylene terephthalate), PETØManufacture ?

ØPropertiesØTm = 250 – 265 oC, Tg = 70 oC

ØEconomicsØAs a plastic, 10 – 15 % growth rate per yearØCurrently about $0.55 per poundØHigh recycling rate

C

O

C

O

O CH2 CH2 O

n

Soft drink bottles 60%Other containers 30

Amorphous and crystallized 10

Uses of PET

23. Definition and ClassesØHard = high modulus (steep slope)ØTough = high elongationØStrong = moderate elongation and high modulus

High High High High High density polyethyleneCellulosicsPolyamides (Nylon)PolyestersPolypropyleneEngineering plasticsPolyacetal, polycarbonate

Hard and tough

Polyimide, polyphenylene sulfide, polyphenylene oxidePolysulfone

High High High Moderate

Poly(vinyl chloride) PVCImpact polystyrene

Hard and strong

Styrene-acrylonitrile

Elongation at Break Examples

Class of Plastic Modulus

Yield Stress

Ultimate Tensile

Strength

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25. Important PlasticsØHard and strongØPoly(vinyl chloride), PVCØManufacture ?

ØPropertiesØTm = 140 oC, Tg = 70 – 85 oCØLow crystallinityØGood chemical resistanceØDegraded by heat and light (Why?)ØExpected to be brittle or pliable at 0 oC?ØBecomes soft, tough polymer with 1-2 wt % plasticizerØPlasticizer = dioctyl phthalateØPlasticized PVC

(CH2 CH)n

Cl

26. Important PlasticsØHard and strongØPoly(vinyl chloride), PVC

ØPlasticized PVC used in medical bags and tubingØEconomicsØAbout 14 billion pounds produced in 2001ØCurrently about $0.36 per poundØCommercial value = $5.0 billionØGood growth rate in recent years (6.4 % per year) except

2000-2001ØEconomics tied to which industry?

(CH2 CH)n

Cl

Construction 76%Consumer goods 6

Electrical fittings, wire and cable 4Home furnishings 2

Miscellaneous 4

Uses of PVCSiding, roofing, gutters, water pipes, flooring

Credit cards

27. Definition and ClassesØSoft = low modulus (shallow slope)ØTough = high elongationØWeak = moderate elongation

Low Low High

Low density polyethyleneLinear low density PEPlasticized PVCIonomer

Low Low Low Moderate

Polyethylene waxes

Class of Plastic Modulus

Yield Stress

Ultimate Tensile

StrengthElongation

at Break Examples

Soft and weak

Soft and tough

Low yield

28. Important PlasticsØSoft and ToughØLow-Density Polyethylene, LDPEØManufacture ?

ØPropertiesØHigh degree of branchingØ60 branches per 1000 carbons – How are these formed?

ØTm = 115 oC, lower than HDPE and LLDPEØLow crystallinity ⇒ high clarity for filmsØGreater permeability to gases than HDPEØDensity between 0.90 and 0.94 g/ccØReadily processed (flows well when molten)

(CH2 CH2)n

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29. Important PlasticsØSoft and ToughØLow-Density Polyethylene, LDPE

ØEconomicsØ6.9 billion pounds produced in 2001ØCurrently about $0.49 per poundØCommercial value = $3.4 billionØFlat consumption due to competition from (substitution by)

LLDPE

(CH2 CH2)n

Film 59%Extrusion 17

Injection molding 6Wire and cable 4

Adhesives and sealants 4Miscellaneous 10

Uses of LDPEPackaging, trash bagsPaper coatingsSqueeze bottles, toys

30. Important PlasticsØSoft and ToughØLinear Low-Density Polyethylene, LLDPEØManufacture ?

ØPropertiesØModerate degree of branching due to occasional insertion of

comonomerØHigher melting, lower clarity than LDPEØMore or less crystalline???

ØHigher tensile strength (stronger) than LDPEØDensity between 0.91 and 0.94 g/cc

31. Important PlasticsØSoft and ToughØLinear Low-Density Polyethylene, LLDPE

ØEconomicsØ7.6 billion pounds produced in 2001ØCurrently about $0.39 per poundØCommercial value = $3.0 billionØHigh growth rate (7.4 % per year, except for 2000-2001),

mainly by replacing LDPE

Shrink wrap, packaging, heavy duty trash bags

Film 72%Injection molding 9

Rotational molding 6Wire and cable 3Miscellaneous 10

Uses of LLDPE

32. The Three PE’sØComparison of the three PE’s

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33. The Three PE’s

HDPE

Few short chain branches (SCB)

LLDPESCB : YES

LDPESCB: YESLCB: YES

cross-links

highly crystalline polymer

amorphouspolymer

semi-crystalline

Note the way the polymer strands pack together

Which polymer is most flexible? Why?

34. The Three PE’sØStress-strain curves – Which is which?

35. Definition and ClassesØHard = high modulus (steep slope)ØBrittle = low elongation

High High Low

PolystyrenePoly(methyl methacrylate)Unsaturated polyester resinsEpoxy resins

Elongation at Break ExamplesModulus

Yield Stress

Ultimate Tensile

Strength

Phenol-formaldehyde, urea-formaldehyde and melamine- formaldehyde resins

Class of Plastic

Hard and brittle

No well-defined

yield

36. Important PlasticsØHard and brittleØPolystyrene, PSØManufacture

ØPropertiesØTm = 227 oC, Tg = 94 oCØAmorphous, low crystallinityØFlammableØYellows in light – requires UV stabilizationØWhy is this polymer unstable to light?

(CH2 CH)n

r10

37. Important PlasticsØHard and brittleØPolystyrene, PS

ØEconomicsØ2.5 % growth rate from 1990 – 2000, -11% from 2000-2001 ØAbout 6.1 billion pounds produced in 2001ØCurrently about $0.52 per poundØCommercial value = $3.2 billion

(CH2 CH)n

Packaging and one-time use 48%Electrical and electronics 17

Construction 13Consumer products 9

Medical products 7Miscellaneous 6

Uses of PS

Clear clam shells

38. Plastics EconomicsØPlastics Material and Resin ManufacturingØ11 % of total for all of Chemical Manufacturing

ØHigh growth rate relative to other polymers

$0

$10

$20

$30

$40

$50

70 75 80 85 90 95

Year

Bill

ions

of D

olla

rs

Plas. Matls & ResinsOrg. Fib.-Noncell.

Synthetic Rubber

Org. Fib.-Cellulosic

39. Plastics EconomicsØRecent growth rates

PlasticsPolyethylene Low density 7.575 -1.6% 6.94 -8.4% 0.5% Linear low density 7.951 -1.9 7.63 -4.0 7.4 High density 13.968 0.8 12.479 -10.7 5.3Polypropylene 15.739 1.6 15.837 0.6 6.5Styrene Polymers Polystyrene 6.844 5.8 6.106 -10.8 2.5 Styrene-acrylonitrile 0.128 4.1 0.127 -0.8 -0.5 Acrylonitrile-butadiene-styrene & other 3.120 0.7 2.725 -12.7 2.9Polyamide 1.281 -5.5 1.039 -18.9 8.6Polyvinyl chloride & copolymers 14.442 -3.2 14.257 -1.3 4.7Epoxy 0.693 7.5 0.610 -12.0 3.5Total 71.741 -0.05% 67.75 -5.6% 4.60%

2000 Billion

lb

Annual Change 1999-00

Annual Change 1990-00

Polymer2001

Billion lb

Annual Change 2000-01

“Facts and Figures for the Chemical Industry”, C&E News, June 24, 2002, p. 63-64

40. Plastics EconomicsØGrowth Rates, except for 2000 – 2001ØHDPE = 5 % AAGRØLLDPE = 7 - 8 % AAGR – slightly higher than PPØLDPE = 0.5 % AAGR

0

2

4

6

8

10

12

14

16

89 90 91 92 93 94 95 96 97 98 99 00 01

Year

Bill

ions

of P

ound

s

HDPE

LDPE

LLDPE10.7 %

4.0 %

8.4 %

r11

41. Requirements for FibersØHigh tensile strength (tenacity)ØPliable but low elongationØAbrasion resistantØHigh melting point (esp. for clothing)ØTm > 200 oC (iron without damage) but < 300 oC to

enable spinning from meltØTg < 100 oC so fibers soften when ironed at 150 oCØCreases removed

Polymer Tg (oC) Tm (oC)

PET 70 265Nylon 6,6 60 265

PAN 105 320PP -5 165

42. Requirements for FibersØFibers are pulled (drawn) during spinningØMelt spinningØWet spinning (polymer dissolved in solvent,

filaments extruded into non-solvent)ØDry spinning (polymer dissolved in solvent, solvent

evaporates)

ØDrawing orients amorphous regions, stronger fibers resultØDrawing makes fibers much stronger in

direction of draw than across it (anisotropic)

43. Spinning of Fibers 44. Requirements for FibersØSymmetrical, unbranched polymerØHigh crystallinity promotes linear molecular

alignment – this is critical ØHigh cohesive energy (intermolecular forces)

ØStrong intermolecular forces promoteØHigh tenacity, fiber strength, low elongation

CH

O

H

O H

CH

C N

H

O

H

NC

O

C O

O

C O

O

CH

C N

NC

CH

hydrogen bonding: dipole-dipole:

cellulosics proteins, nylons polyesters acrylics

δ-

δ+

δ-

δ+

δ-

δ+

δ-δ+

r12

45. Requirements for FibersØRigid backbone

structuresØAramids (aromatic

polyamides)Øhigh stiffnessØheat resistance

ØCompete with wire and glass fibersØForm rodlike

polymers

CH2

CH2CH2

CH2NH

CCH2

O

CH2CH2

CH2C

CH2CH2

NH

O

NH NHC

CH2

CH2

CH2

CH2O

CO

n

n

NH NHC

O

C

nO

NH NH C

O

C

n

O

46. Requirements for FibersØRank these fibers by strength

C CH2CH2

CH2CH2

CO

O O

CH2CH2

O

C CO

O OCH2

CH2

O

n

n

C

O

CO

OCH2

CH2

O

n

47. Important FibersØNylon

ØManufactureØNylon 6,6 formed by condensation polymerization between

adipic acid and hexamethylenediamineØ280 – 300 oC under vacuumØAcetic acid terminates chains, controls Mw

ØPropertiesØDyeableØStrong, hard wearing fiberØWithstands high temperatureØHydrophobic

NH (CH2)5 C

O

nnylon 6

C

O

(CH2)4 C

O

NH (CH2)6 NHn

nylon 6,6

48. Important FibersØNylon

ØEconomicsØProduction relatively flat for past 15 yearsØ2.6 billion pounds produced in 2000ØNylon 6,6 is two-thirds of US market, nylon 6 is one-thirdØCarpet and rug markets increasing, other applications

decreasing

NH (CH2)5 C

O

nnylon 6

C

O

(CH2)4 C

O

NH (CH2)6 NHn

nylon 6,6

Carpets and rugs 74%Industrial 16Apparel 10

Uses of Nylon

Belts, hoses, tire cords

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49. Important FibersØPolyesterØManufactureØInitial formation of oligomers by:ØReaction of TPA and ethylene glycolØReaction of DMT and ethylene glycol

ØPolymerization at 200 – 290 oC in vacuo with SbO3 catalystØFibers melt spun like nylon at about 260 oC

ØPropertiesØReadily blended with other fibers (cotton)ØChoice of phthalate can vary tensile and elongation

propertiesØHydrophobic (does not absorb water)ØStains easilyØStatic charge

C

O

C

O

O CH2 CH2 O

n

50. Important FibersØPolyester

ØEconomicsØLargest volume fiber producedØ3.9 billion pounds produced in 2000 ØLarge production increases in 1970’sØRoughly same amount produced in 1980 and in 2000ØDecreased slightly from 1980 – 1990Ø Increased slightly from 1990 – 2000

C

O

C

O

O CH2 CH2 O

n

Clothing 50%Home furnishings 20

Industrial 30

Uses of Polyester

51. Important FibersØPolyolefinØManufactureØIsotactic polypropylene prepared by Ziegler-Natta

catalyzed polymerizationØSome HDPE (from Ziegler-Natta catalysis) for

monofilamentsØFibers produced by melt spinningØFiber strength achieved by high molecular weightØOnly weak intermolecular forces (van der Waals)

ØPropertiesØLow density (0.91 g/cc) yield lightweight fiberØChemical and abrasion resistanceØGood insulating propertiesØNot easily dyed

(CH2 CH)n

CH3

(CH2 CH2)n

52. Important FibersØPolyolefinØUsesØIndustrial (rope, belts, carpet backing awnings)ØHome textile (floor covering, upholstery fabric, blankets)ØApparel (sportswear, hosiery)ØDiapers (nonwoven fibers)

ØEconomicsØLargest growth segment within fibersØSteady growth of 6 – 8 % per year since 1982ØSurpassed nylon in 1998ØClosing in on polyester as the highest production fiber

(CH2 CH)n

CH3

(CH2 CH2)n

r14

53. Fiber ProductionØPolyester most important synthetic fiberØPolyolefins are rising star (PP)ØHighest growth rate – nearly 6% per year

0

2

4

6

8

10

12

70 75 80 85 90 95 00

Year

Bill

ions

of P

ound

s

CottonPolyesterPolyolefinsNylonAcrylics

54. Important Fibers

55. Properties of ElastomersØRequirements for ElastomersØCompletely amorphous, used above their TgØLow intermolecular forces allow for flexibilityØHigh modulus and strength when stretchedØOften crystallize when stretched

ØLarge reversible extensions (several hundred percent) ØHigh localized chain movements, low overall movement of chains

relative to one anotherØCross-linked chains prevent slippage

slip

stressapplied

Stressremoved

56. Properties of ElastomersØPossess high molar mass to allow chain

entanglements or are cross-linkedØGives dimensional stability

ØCross-linked with sulfurØReaction at allylic hydrogens

CH2

C

H3C

C

H

CH2

Sx

CH2

C

H2C

C

H

CH2

Sy

CH2

C

H2C

C

H

CH2

n

n

n

y = 1 or 2

r15

57. Important ElastomersØNatural Rubber, NRØCis-1,4-polyisoprene

ØPolybutadiene, BR

CH3

C C

H

CH2)n(CH2

Biological polymerizationAgricultural cropTg = -70 oCPrimary use is auto tires2.2 billion lb/yr – all imported

Free-radical polymerizationPrimary use is auto tiresAlso belts, hoses, gaskets1.33 billion lb/yrTg = -110 oC

H

C C

H

CH2)n(CH2

Why is the Tg 40 oC lower than that of natural rubber?

58. PolybutadieneReaction:

nCH2 CH CH CH2 (CH2 CH CH CH2)n

1,3-butadiene polybutadiene

Mechanism:

(1) ROOR 2RO

(2)

(3)

RO + CH2 CH CH CH2

RO CH2 CH CH CH2 + CH2 CH CH CH2

RO CH2 CH CH CH2 CH2 CH CH CH2

then (3), (3), (3), etc.

Vulcanization:

(CH2 CH CH CH2)n (CH2 CH CH CH)n

S

S

(CH2 CH CH CH)n

RO CH2 CH CH CH2

S∆

59. Important ElastomersØNatural Rubber, NRØCis-1,4-polyisoprene

ØStyrene-Butadiene Rubber, SBR

CH3

C C

H

CH2)n(CH2

Biological polymerizationAgricultural cropTg = -70 oCPrimary use is auto tires2.2 billion lb/yr – all imported

Free radical polymerizationMechanism???

Tg = -65 oCPrimary use is auto tiresCompetes with NR1.93 billion lb/yr

(CH2 CH CH CH2)n (CH2 CH)n

60. CopolymerizationØMany important elastomers like SBR are

random copolymersØSequence of monomer insertion is completely

randomØRandom arrangement of styrene and butadieneØSBR (styrene-butadiene rubber)ØCopolymer with 6:1 butadiene:styrene composition

nCH2 CH

+ > nCH2 CH CH CH2

CH2 CH CH2 CH CH CH2 CH2 CH CH CH2

r16

61. CopolymerizationØAnother important elastomer is formed by

random polymerization of three monomersØAcrylonitrile, butadiene, and styreneØABS = acrylonitrile-butadiene-styrene terpolymer

ØThree monomers need not be present in the same amount

CH2 CH

CN

+ CH2 CH CH CH2 + CH2 CH

CH2 CH CH2 CH CH CH2 CH2 CH

CN

62. Important ElastomersØEthylene-Propylene

Diene Monomer, EPDM

ØPolyisobutylene, Butyl Rubber

Ziegler-Natta catalystRandom arrangement of C2

and C3 units creates highly flexible polymer

Diene provides reactive sites for cross-linking

0.76 billion lb/yr

Cationic polymerizationMechanism?Isoprene used to cross-linkPrimarily used for tubes

and tires

(CH2 CH2)n (CH2 CH)n

CH3

CH CH3

dimer =diene

(CH2 C)n

CH3

CH3

(CH2 C

CH3

CH CH2)1